Managing Serviceguard Eighteenth Edition, September 2010

because that provides the best chance for a successful failover (and failback) if pkg1
fails.
But you also need to weigh the relative importance of the packages. If pkg2 runs a
database that is central to your business, you probably want it to run undisturbed, no
matter what happens to application packages that depend on it. In this case, the database
package should have the highest priority.
Note that, if no priorities are set, the dragging rules favor a package that is depended
on over a package that depends on it.
Consider assigning a higher priority to a dependent package if it is about equal in
real-world importance to the package it depends on; otherwise assign the higher priority
to the more important package, or let the priorities of both packages default.
You also need to think about what happens when a package fails; see “What Happens
when a Package Fails” (page 186).
Extended Dependencies
To the capabilities provided by Simple Dependencies (page 179), extended dependencies
add the following:
• You can specify whether the package depended on must be running or must be
down.
You define this condition by means of the dependency_condition, using one of the
literals UP or DOWN (the literals can be upper or lower case). We'll refer to the
requirement that another package be down as an exclusionary dependency; see
“Rules for Exclusionary Dependencies” (page 185).
• You can specify where the dependency_condition must be satisfied: on the same
node, a different node, all nodes, or any node in the cluster.
You define this by means of the dependency_location parameter (page 295), using
one of the literals same_node, different_node, all_nodes, or any_node.
different_node and any_node are allowed only if dependency_condition is UP.
all_nodes is allowed only if dependency_condition is DOWN.
See “Rules for different_node and any_node Dependencies” (page 186).
For more information about the dependency_ parameters, see the definitions starting
with “dependency_name” (page 294), and the cmmakepkg (1m) manpage.
184 Planning and Documenting an HA Cluster